In field-drains in the grass-covered areas of sports facilities, the distance between the drains varies from 8-10 meters. Uneven drying can be observed at present on many fields. At 2-4 meters from the line of the drain the field is considerably drier than in the areas between the drains.
Fields equipped with various kinds of piping are presented in the German application and Patent Publications DE-P-924931, DE-2059383, DE-H-27 38 133, and DE-H-2840389. By means of a network of pipes beneath the surface of the field it is both warmed, and dried by draining excess water into field-drain soakaways. The warming of the field takes place by blowing warmed air into the pipe network, from which it travels upwards to the surface of the field. The problem with the above-mentioned field constructions is firstly the unevenness of the blowing if the network of pipes is not very dense. Secondly, the back and forwards flow causes fine material substances to enter the known field pipes.
The use of electrical resistances or heating pipes in the surface of a sports field is also known, these both warming and drying the surface of the field. The distance between the resistances or pipes has been only about 20 cm, which has led to an enormous total length of resistance cables and heating pipes.